Index: src/where.c
==================================================================
--- src/where.c
+++ src/where.c
@@ -3484,11 +3484,12 @@
     ** The ANALYZE command and the sqlite_stat1 and sqlite_stat3 tables do
     ** not give us data on the relative sizes of table and index records.
     ** So this computation assumes table records are about twice as big
     ** as index records
     */
-    if( (pc.plan.wsFlags&~(WHERE_REVERSE|WHERE_ORDERED))==WHERE_IDX_ONLY
+    if( (pc.plan.wsFlags&~(WHERE_REVERSE|WHERE_ORDERED|WHERE_OB_UNIQUE))
+                                                              ==WHERE_IDX_ONLY
      && (pWC->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
      && sqlite3GlobalConfig.bUseCis
      && OptimizationEnabled(pParse->db, SQLITE_CoverIdxScan)
     ){
       /* This index is not useful for indexing, but it is a covering index.